Ion implantation causes degradation of electrical properties, such as mobility and minority carrier lifetime. Measures must be taken to heal some or all this ion implanted-related damage. A method of healing such ion implanted-related damage includes thermal treatment at proper conditions, i.e., temperature, time, and ambient gas. In a conventional CMOS process flow, after shallow trench isolation (STI) formation and before input/output (I/O) gate oxide formation, there are several ion implantation steps. Ion implantation steps include, e.g., threshold voltage adjustment, channel stop, and well implantation. The ion implantation process introduces damage in the core active area which degrades transistor performance and reliability.
One method to heal the ion-implant related damage is to use thermal treatment. This thermal treatment is performed prior to the I/O gate oxide formation. Typical conditions to heal the ion-implant related damage are 1050° C. in N2/O2 for approximately 30 seconds. However, as devices dimensions are scaled downward, more effort is required to optimize thermal treatments to further improvement device performance and reliability.
Accordingly, the present invention solves these and other problems of the prior art ion-implantation related damage to a core gate of a transistor.